This application claims the benefit of Japanese Patent Application Number 2006-150498 filed on May 30, 2006, the entirety of which is incorporated by reference.
1. Field of the Invention
The present invention relates to a pallet exchanging device which is installed in front of a working machine such as a vertical machining center and exchanges pallets on which works are placed.
2. Description of the Related Art
Conventionally, working machines such as a vertical machining center are provided with a pallet exchanging device, which exchanges a pallet which is provided in a standby position and on which a work before machining is placed (hereinafter, pre-machining pallet) and a pallet which is provided in an exchanging position (or machining position) and on which a machined work is placed (hereinafter, post-machining pallet), in proximity positions.
Such a pallet exchanging device includes a device disclosed in Japanese Patent Application No. 2005-132876 proposed by the same applicant of the invention in which an arm having a pair of forks facing opposite directions is provided so as to be revolvable and slidable to a front-rear direction with respect to a working machine main body. The pallet exchanging device is installed on a front side of the working machine main body provided with a spindle device or the like of the working machine. After the post-machining pallet in the exchanging position of the working machine main body is received by means of a sliding operation to the front-rear direction, the positions of the pre-machining pallet in the standby position and the post-machining pallet are reversed by the revolving operation, and the pre-machining pallet is placed in the exchanging position again by the sliding operation. When a worker accesses to the working machine main body for machining observation, cutting tool checking, measurement of machined products in machining of first product, the paired forks are revolved to face a right-left direction with respect to the working machine main body so that the operator is not disturbed by the pallet exchanging device. As a result, a working space can be secured on the front side of the working machine main body (namely, on the front side of a machining space).
On the other hand, pallet exchanging devices other than the above-described pallet exchanging device include a device disclosed in Japanese Utility Model Laid-Open No. 6-63252, for example. The pallet exchanging device 51 described in the Japanese Utility Model Laid-Open No. 6-63252 is explained with reference to FIG. 11. FIG. 11 is an explanatory diagram illustrating the pallet exchanging device 51 viewed from above. An up-down direction in FIG. 21 will be described as a right-left direction of the pallet exchanging device 51, a right-left direction in FIG. 11 will be described as a front-rear direction of the pallet exchanging device 51 in the description.
The pallet exchanging device 51 is provided to a front side of a plurality of working machines 50, 50 which are arranged in parallel in the right-left direction, and exchanges a pre-machining pallet 58a stored in a work storage rack 57 and a post-machining pallet 58b in the exchanging position (working position) of the working machine. The pallet exchanging device 51 has a rail 52 which are protruded to the right-left direction on the front side of the working machines 50, 50, and a movable platen 53 which slides along the rail 52. The movable platen 53 is provided with a revolving table 54 which horizontally revolves around a vertical axis, and the revolving table 54 is provided with an arm 55 having a pair of forks extensible to opposite directions. The arm 55 is movable to a vertical direction by means of lifting and lowering devices 56, 56. The work storage rack 57 has a plurality of pallet placing shelves in the vertical direction, and a plurality of works W, W . . . can be stored in one tier so as to be adjacent each other.
In such a pallet exchanging device 51, exchange between the pre-machining pallet 58a on which the work W before machining is placed and the post-machining pallet 58b on which the machined work is placed is performed, by means of the sliding operation of the movable platen 53 to the right-left direction, the lifting/lowering operation of the arm 55 to the vertical direction, and the revolving operation of the revolving table 54.
As described above, when the pallet exchanging device is provided to the front side of the working machine main body, it is a problem of securing a working space for a worker in front of the working machine main body. According to the pallet exchanging device which was proposed by the same applicant of the invention, the working space is tried to be secured by revolving the arm. However, since the length of the arm is limited in view of strength, the working space which is secured by revolving the arm is also limited. In the pallet exchanging device which was proposed by the same applicant of the invention, therefore, the sufficient working space for the worker cannot be secured according to working contents or the like. Since the arm can slide only to the front-rear direction with respect to the working machine, the pallet exchanging device cannot cope with a multi-phase pallet exchanging system described in the Japanese Utility Model Laid-Open No. 6-63252.
On the other hand, in the pallet exchanging device 51 described in the Japanese Utility Model Laid-Open No. 6-63252, although the sufficient working space can be secured on the front side of the working machine main body, since the works W, W . . . are stored to be arranged in the right-left direction in the work storage rack 57, the rail 52 for sliding the movable platen 53 should be projected to the right-left direction, thereby arising a problem such that the device becomes large. According to the growing in size of the pallet exchanging device 51, when the pre-machining pallet 58a at the end of the work storage rack 57 is exchanged, it takes a long time for the exchanging operation, thereby deteriorating machining efficiency of the work W.
The present invention is devised in view of the above problems, and its object is to provide a pallet exchanging device which can secure a sufficient working space and can cope with a multi-phase pallet exchanging system without increasing the size of the device.